Will I Have Problems With a Medium Cage SRAM X-7 RD and a 11-26 Cassette?

I'm in the process of upgrading my old mountainbike from a 7 speed to a 9 speed. I just purchased a SRAM X-7 medium cage rear derailleur, X-7 front derailleur, and X-9 trigger shifters. Since I'm going to be riding it almost exclusively on relatively flat roads, I decided to get a tighter cassette - it's an 11-26. But right after I made the purchase, I began to worry if it would work, because nearly all of the MTB cassettes I've seen were quite a bit larger - usually 11x34 or so. This cassette seems more like it's made for a road bike (though it is a 9 speed SRAM). Will this be a problem?

The cassette will work... you might find it desirable to shorten your chain a little bit when you put the new cassette on, if that is the only one you'll be using with your bike. Aside from that you should have no problems...